Winding – tensioning – or guiding – Reeling device – With spring motor
Patent
1996-09-12
1998-03-24
Jillions, John M.
Winding, tensioning, or guiding
Reeling device
With spring motor
B60R 2246
Patent
active
057303843
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a coupling between the belt drum of a belt retractor and a belt pretensioner rotary drive, which has an output shaft.
In order to ensure that normal rotation of the belt drum of a belt retractor is not hindered by the rotary drive of the belt pretensioner the belt drum is kept uncoupled from the belt pretensioner rotary drive until the latter is activated. On the other hand the belt drum should be able to be freely rotated after the safety belt has been pretensioned to ensure that the normal take-up and locking function of the belt retractor is available again, and for instance following a slight accident, that the vehicle user is able to re-fasten his or her safety belt and drive to a repair facility.
Among the various possible designs of couplings ratchet couplings have the advantage of being able to be simply released again by rocking the coupling pawls back into their initial position. In the case of known couplings the coupling pawls are surrounded by an internally toothed coupling wheel and are pivoted outward in order to produce the coupling connection. So far it has been considered to be an advantage for the coupling annulus or ring to be arranged radially outside the coupling pawls, since there is more space available for the teeth radially outside than inside and larger teeth are possible while having a finer tooth pitch.
The invention is based on the fact that force transmission from a coupling pawl to a coupling wheel placed radially outside leads to problems to the extent that the coupling wheel is subjected to a locally concentrated load with a high radial component. The peripheral acceleration of a belt pretensioner rotary drive reaches values of the order of 1000 g and more so that the components of the coupling are subjected to extremely high loads. Such components have consequently always been manufactured of materials such as steel, with a high mechanical strength. These materials are however not only expensive but also involve a large mass, something which in turn leads to high inertial forces, which must be overcome by having a high drive power.
The invention is to provide a coupling, whose components are subject to lesser loads so that they may be produced using a light metallic constructional material. In accordance with the invention the belt drum possesses an externally toothed coupling wheel; on the output shaft a drive disk is connected, which bears at least one pivotally mounted coupling pawl; the coupling pawl is held by a return spring in a neutral position clear of the periphery of the coupling wheel and is able to be pivoted inward into an engagement position in engagement with the coupling wheel. In this coupling the coupling operation takes place radially from the outside to the inside, the internally placed coupling wheel being predominantly loaded in the peripheral direction. Radial components which are still present lead to an easily handled thrust load of the coupling wheel from the outside to the inside. For the components of the coupling it is possible to employ lighter materials of lower strength so that besides a compact design there is also a reduction in inertial forces and a reduction in the drive power required.
A further easing off of requirements as regards mechanical strength of the coupling pawl and its bearing means is achieved by an advantageous further development of the invention, in accordance with which in the engaged setting the coupling pawl is supported by a surface of a support structure on the periphery of the drive disk, more particularly with respect to forces directed in the radial direction of the disk. In the preferred embodiment this support structure possesses a high mechanical rigidity, since it is constituted by a continuous ring which is formed on the periphery of the drive disk and extends axially from the disk body.
In an advantageous embodiment the extremely high angular acceleration occurring on activation of the rotary drive of the belt pretensioner is utilized for control of the coupling pawl by using its
REFERENCES:
patent: 4428846 (1984-01-01), Fohl
patent: 4568037 (1986-02-01), Kawaguchi et al.
patent: 4991790 (1991-02-01), Fohl et al.
Jillions John M.
TRW Occupant Restraint Systems GmbH
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